New synthesis method for ternary metal oxide photoelectrodes

Developing facile and environmentally friendly approaches to prepare semi-transparent ternary oxide thin film photoelectrodes is an important goal for solar fuel production via the photoelectrochemical water splitting tandem cell. However, different materials typically require very different synthesis conditions, and these conditions often require harsh solvents and processing. Herein the LIMNO lab reports a novel synthesis route that employs ethylenediamine tetra-acetic acid (EDTA) to enable compatible water solubility of diverse metal cations, which affords transparent films via solution processing. Using BiVO₄ as a model material, we demonstrate a remarkable improvement in transparency quantified by the direct transmittance at 600 nm of >80% vs. the < 10% observed with state-of-the-art electrodeposited thin films while maintaining reasonable solar-driven oxidation photocurrents (1.75 mA cm^-2 in the presence of a sulphite hole scavenger). Furthermore, we demonstrate that the synthesis technique can be applied in a general fashion towards the synthesis of diverse n- and p-type metal oxide materials, such as ZnFe₂O₄ and CuFeO₂. The paper detailing the results, published in ChemSUSChem, was chosen as a Very Important Paper by the editors, based on the enthusiasm of the reviewers. Indeed, this improvement will help to rapidly advance the field of ternary oxide thin film photoelectrodes.